<PAGE>
                                                                    Exhibit 10.1



                                    SUBLEASE

         This SUBLEASE is made as of __March 16_________, 2004, by and between
ANTIGENICS INC. ("Sublessor"), f/k/a Aquila Biopharamaceuticals, Inc., a
Massachusetts corporation having a place of business at 3 Forbes Road,
Lexington, Massachusetts 02421, and PP Manufacturing Corporation ("Sublessee"),
a Delaware corporation having a place of business at 175 Crossing Boulevard,
Framingham, Massachusetts 01702 and which is a wholly owned subsidiary of VIRBAC
S.A., a French corporation.

                              W I T N E S S E T H:
                              --------------------

         WHEREAS, pursuant to that Lease dated as of September 19, 1997 between
NDNE 9/90 Corporate Center LLC, as landlord ("Prime Lessor") and Sublessor, as
tenant (as amended, the "Prime Lease"), a true and complete copy of which is
attached hereto as EXHIBIT A, Sublessor leases approximately 41,020 rentable
square feet of floor space on the first, second and third floors of the building
known as and numbered 175 Crossing Boulevard, Framingham, Massachusetts (the
"Building") all as more particularly described in the Prime Lease (the
"Premises"); and

         WHEREAS, Sublessee desires to sublease a portion of the Premises from
Sublessor, and Sublessor is willing to sublease the same, all on the terms and
conditions hereinafter set forth;

         NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties covenant and agree as
follows:

         1. Sublease of Premises. For the rent and upon the terms and conditions
herein set forth, Sublessor hereby subleases to Sublessee, and Sublessee hereby
subleases from Sublessor, 21,132 rentable square feet of floor space on the
first and second floors of the Building (the "Subleased Premises" as shown on
EXHIBIT B attached hereto and made a part hereof. Sublessor shall have the right
(which shall be personal to it and its employees) from time to time to access,
occupy and use as an invitee of Sublesee the R&D Office No. 252 (the "R&D
Office") for a period from the date hereof until April 2, 2004; provided,
however, that such access, occupancy and use of the R&D Office and such access
through the Access Passage, (i) may only occur during regular business hours,
except in the event of an emergency, (ii) shall be subject to the reasonable
rules and regulations of Sublessee (including, without limitation, any security
and identification requirements) and (iii) may not unreasonably interfere with
Sublessee's use and occupation of the Subleased Premises or the conduct of its
business therein. Sublessor hereby agrees to indemnify and hold harmless
Sublessee from and against all claims, damages, losses, liabilities, costs and
expenses, including, without limitation, attorneys' fees, with respect to any
and all activities of Sublessor carried out in connection with its access to the
R&D Office.


<PAGE>

         2. Term. The term of this Sublease (the "Term") shall commence upon the
date on which this Sublease has been fully executed by Sublessor and Sublessee
and the Prime Lessor has delivered the "Consent" as hereinafter defined (the
"Commencement Date"), and shall, unless earlier extended as herein set forth,
expire at 11:59 p.m. on September 30, 2010 (the "Expiration Date") or such
earlier date upon which said term may expire, be canceled or be terminated
pursuant to any of the terms or provisions of the Prime Lease, this Sublease or
applicable law.

         3. Appurtenant and Reserved Rights. Sublessee shall have, as rights
appurtenant to the Subleased Premises, the non-exclusive right in common with
others in the Building to use the common areas of the land and the Building, as
and to the extent Sublessor is permitted to use the same under the Prime Lease,
except that as to parking, Sublessee shall only have the non-exclusive right in
common with others to use four (4) parking spaces per each even 1,000 square
feet of the Subleased Premises. Sublessor for itself, its successors and assigns
and the Prime Lessor, reserves the right for such parties and their designees to
pass and repass through the Subleased Premises to access the utility area and
any utility service distribution network located in the Subleased Premises that
services the Premises for the testing, repair, maintenance and replacement of
utilities and provision of utilities and services therefrom; provided, however,
that access to the utility area and any utility service distribution network,
(i) may only occur during regular business hours with prior notice, except in
the event of an emergency and (ii) shall be subject to the reasonable rules and
regulations of Sublessee (including, without limitation, any security and
identification requirements). Sublessor for itself, its successors and assigns
and the Prime Lessor, also reserves the right for such parties and for other
sublessees and users of the Premises to pass and repass along the central
corridor to and to use the freight elevator and the restrooms in the locations
shown as the "Central Corridor Area" on EXHIBIT C attached hereto; provided,
however, that such access to the Central Corridor, (i) may occur twenty four
hours a day, seven days a week and (ii) shall be subject to the reasonable rules
and regulations of Sublessee (including, without limitation, any security and
identification requirements).

4. Base Rent. Sublessee shall pay to Sublessor the following amounts annually as
base rent (the "Base Rent"):

<TABLE>
<CAPTION>
         ---------------------------------------------------------- ---------------------------
         Dates                                                         Base Rent
         ---------------------------------------------------------- ---------------------------
<S>                                                                   <C>
         Commencement Date until September 8, 2006 (the end of         $ 483,500.16 per
         year the 8th lease year under the Prime Lease)
         ---------------------------------------------------------- ---------------------------
         From September 9, 2006 (the beginning of the 9th lease        $ 515,198.16 per year
         year) until Expiration Date
         ---------------------------------------------------------- ---------------------------
</TABLE>

         In addition, Sublessee shall pay as additional rent hereunder
("Additional Rent") Sublessee's Share (as hereinafter defined) of amounts from
time to time payable by Sublessor as "Tenant" as Additional Rent under the Prime
Lease, including without limitation amounts for Real Estate Tax Escalation,
Operating Cost Escalation and Park Common Expenses, in each case as defined in
the Prime Lease. "Sublessee's Share" is 51.52% of what Sublessor is

                                      -2-
<PAGE>

obligated to pay for such costs. Because Sublessor pays 35.22% of such costs
("Tenant's Proportionate Share" in the Prime Lease), Sublessee is required to
pay 18.15% of the total of such costs under the Prime Lease. In addition, either
(a) Sublessee shall pay as Additional Rent an allocation of amounts due for
payment for electricity, water, gas, HVAC and other utility charges with respect
to the Subleased Premises as equitably determined by Sublessor and Sublessee or
(b) at Sublessor's election, the Subleased Premises shall be separately metered
at Sublessor's sole cost and expense and Sublessee shall pay all utility charges
directly to the utility providers.

         Base Rent shall be due and payable in equal monthly installments in
advance on the date that is five (5) days before the first day of each calendar
month without demand, deduction, offset or abatement, at the address of
Sublessor, or at such other place as Sublessor may designate. Base Rent shall be
pro rated for any partial month. Sublessee shall pay monthly estimates of
Operating Cost Escalation. Real Estate Tax Escalation and Park Common Expenses,
as applicable from time to time, on the date that is five days prior to the
first day of each calendar month. Sublessee shall pay all other Additional Rent
to Sublessor not less than five (5) business days after demand from Sublessor.

         5. Permitted Uses. Sublessee shall use the Subleased Premises only for
the uses permitted by the Prime Lease. Without limiting any other term or
provision hereof, Sublessee shall not do, suffer or permit anything to be done
in or upon the Subleased Premises except in accordance with and as permitted by
the Prime Lease and applicable law. Sublessor shall from time to time upon
Sublessee's request notify Prime Lessor of substances to add to Exhibit "O" to
the Prime Lease that Sublessee has notified Sublessor are to be used in the
ordinary course of Sublessee's business at the Premises.

         6. Condition of Subleased Premises. Sublessee acknowledges that it has
inspected the Subleased Premises and agrees to accept the Subleased Premises in
their present "as is" condition without representation or warranty of any kind
by Sublessor, provided, however, that Sublessor represents and warrants that to
its knowledge, the Subleased Premises are, as of the date of this Sublease, in
the condition required by the Prime Lease in all material respects. Sublessee
shall not in any way make any alterations, additions or improvements to the
Subleased Premises without having first secured the written permission of
Sublessor and Prime Lessor. Any work shall be done in accordance with the plans
and specifications submitted to and approved by Sublessor and Prime Lessor.

         Any alterations, additions or improvements made by Sublessee to the
Subleased Premises shall be done at Sublessee's sole cost and expense in a good
and workmanlike manner using new materials of first-class quality consistent
with the style and finish of the Subleased Premises. Sublessee shall secure all
necessary permits in advance of commencement of any work and shall keep the
Subleased Premises free of any mechanics' or other liens and shall hold
Sublessor and Prime Lessor harmless from any loss, cost or damage arising out of
any work done by Sublessee or its agents or contractors. All contractors working
for Sublessee in the Subleased Premises shall be properly insured and shall
provide certificates of insurance naming Sublessor and Prime Lessor as
additional named insureds prior to commencement of any work. Sublessee, at the
expiration of the Term or earlier termination of this Sublease, shall deliver
the


                                      -3-
<PAGE>

Subleased Premises to Sublessor in the same condition as they were at the
time of the commencement of this Sublease, reasonable wear and tear only
excepted, and including removing any remaining alterations made by Sublessee if
so requested by Prime Lessor or Sublessor, and otherwise in the condition
required by the Prime Lease, and Sublessee shall remove all personal goods and
effects of Sublessee leaving the Subleased Premises neat, clean and in
first-class rentable condition. Sublessee shall be solely responsible for its
own personal property.

         Notwithstanding the foregoing, each of Sublessor and Sublessee, soley
as between themselves and their respective permitted sucessors and assigns
(expressly excluding the Prime Lessor who shall in no way be bound hereby
including in the event of any attornment of Sublessee under this Sublease
directly to the Prime Lessor), hereby agree that in the event the costs of
restoring the Subleased Premises at the expiration or termination of this
Sublease (the "Restoration Costs") exceeds $210,000 (the "Threshold Amount") and
(1) such expiration is at the contemplated expiration of the Term on September
30, 2010 then Sublessor shall pay or otherwise reimburse Sublessee for any
Restoration Costs in excess of the Threshold Amount provided that Sublessor
shall have sole control over and resolve with the Prime Lessor any issues
relating to what items must be removed and/or restored; (2) any termination is
as a result of a default under the Prime Lease caused by Sublessor for which
Sublessee is not responsible and Sublessee is not allowed to holdover in the
Subleased Premises for the balance of the Term by the Prime Lessor then
Sublessor shall pay or otherwise reimburse Sublessee for all Restoration Costs
whether or not the amount of such costs exceeds the Threshold Amount) provided
that Sublessor shall have sole control over and resolve with the Prime Lessor
any issues relating to what items must be removed and/or restored; and (3) any
termination is as a result of a default under the Prime Lease caused by
Sublessor for which Sublessee is not responsible and Sublessee is allowed to
holdover in the Subleased Premises for the balance of the Term by the Prime
Lessor then Sublessor shall pay or otherwise reimburse Sublessee for seventy
percent (75%) of any such costs in excess of the Threshold Amount. Payment by
Sublessor to Sublessee pursuant to this provision shall be made within sixty
(60) days of Sublessor's receipt of written invoice for payment from Sublessee,
accompanied by all reasonable support documention evidencing the amounts owed.

         7. Insurance; Indemnification. Sublessee shall maintain during the Term
hereof liability, property damage and other insurance in such amounts and
coverages and in such form as are required of Sublessor under the terms of the
Prime Lease. All such insurance shall specifically name Prime Lessor and
Sublessor (together with any other party or parties as required under the terms
of the Prime Lease) as additional insureds thereunder. Such insurance shall not
be subject to cancellation, termination or change with respect to Prime Lessor,
Sublessor or such other parties without thirty (30) days' prior written notice.
A duplicate original of the policy, a binder evidencing coverage thereof or a
certificate of such insurance shall be delivered to each of Prime Lessor and
Sublessor.

         Sublessee agrees to protect, defend (with counsel approved by Prime
Lessor and Sublessor), indemnify and hold Sublessor and Prime Lessor harmless
from and against any and all claims, losses and liabilities (other than claims
and liabilities arising from any negligence or willful misconduct of Sublessor
or its agents or employees in or about the Subleased Premises),


                                      -4-
<PAGE>

arising: (i) from the conduct or management of or from any work or thing
whatsoever done in or about the Subleased Premises during the Term hereof; (ii)
from any condition arising, and any injury to or death of persons, damage to
property or other event occurring or resulting from an occurrence in or about
the Subleased Premises during the Term hereof; and (iii) from any breach or
default on the part of Sublessee in the performance of any covenant or agreement
on the part of Sublessee to be performed pursuant to the terms of this Sublease
or from any negligent act or omission on the part of Sublessee or any of its
agents, employees, licensees, invitees or assignees. Sublessee further agrees to
indemnify Sublessor and Prime Lessor from and against any and all damages,
liabilities, costs and expenses, including reasonable attorneys' fees, incurred
in connection with any such indemnified claim or any action or proceeding
brought in connection therewith. Notwithstanding anything in this Sublease to
the contrary (including, without limitation, Sections 7, 9 and 11), Sublessor
agrees that it will not seek to recover consequential damages from Sublessee
under this Sublease unless and then limited to the extent a third party is
seeking to recover consequential damages from Sublessor and Sublessor will not
enforce any judgment for such consequential damages it obtains against Sublessee
except to the extent necessary to pay consequential damages owed to a third
party.

         8. No Assignment or Subletting. Sublessee shall have no right to assign
this Sublease or to sublease the Subleased Premises or any part thereof without,
in each case, Sublessor's and Prime Lessor's prior written consent. For the
purposes of this Sublease the word "assign" shall be defined to include any
direct or indirect change in control of the Sublessee. Sublessor's consent to an
assignment of this Sublease or to a subletting of all or a portion of the
Subleased Premises shall not be deemed a waiver of Sublessor's consent to any
further assignment of this Sublease or subletting of all or a portion of the
Subleased Premises by Sublessee. Notwithstanding any assignment or subsublease
of this Sublease (whether or not permitted hereunder), Sublessee shall remain
fully liable for (and is not relieved or released from) all obligations of
Sublessee under this Sublease.

         9. Primacy and Incorporation of Prime Lease. This Sublease is subject
and subordinate to the Prime Lease and Sublessor purports hereby to convey, and
Sublessee takes hereby, no greater rights hereunder than those accorded to or
taken by Sublessor as tenant under the terms of the Prime Lease. Except as may
be inconsistent with the other provisions hereof, all of the terms and
provisions in the Prime Lease are incorporated herein by reference as if set
forth herein in full and shall be applicable to this Sublease with the same
force and effect as if Sublessor were the landlord under the Prime Lease and
Sublessee were the tenant thereunder. Sublessee and Sublessor agree from and
after the date hereof to comply fully with all such terms, conditions and
obligations of the Prime Lease applicable to the Subleased Premises. Except as
otherwise provided herein, Sublessee covenants with Sublessor to fully and
faithfully perform all of Sublessor's obligations, covenants and conditions
under the Prime Lease to be paid, performed and observed with respect to the
Subleased Premises from and after the commencement of the Term hereof and to
protect, defend (with counsel reasonably approved by Sublessor), indemnify and
hold Sublessor harmless from all acts or failures to act on the part of
Sublessee during the Term hereof. Except as otherwise provided herein, this
Sublease shall in all respects be subject to the Prime Lease and if the Prime
Lease shall terminate during the Term hereof, this Sublease, subject to the
rights of the Prime Lessor under the Consent referred to in Section 17 below,
shall terminate upon such termination date with the same force and



                                      -5-
<PAGE>

effect as if such termination date had been set forth herein as the date of
termination hereof. Sublessor represents, to the best of its knowledge, that as
of the date hereof, no default has occurred under the Prime Lease giving rise
then, or in the future, to the right of Prime Lessor to terminate the Prime
Lease. Notwithstanding anything else to the contrary contained herein, the
following Sections, Exhibits and Definitions of the Prime Lease are not
incorporated herein by reference and are not applicable to this Sublease: (a)
Section 2.3(c) (re-measurements), Section 3 (Commencement Date; Improvements)
(exclusive of Section 3.7(b) (installations), Section 3.8 (general provisions)
and the last sentence of Section 3.10 (Changes in Building or Lot), each of
which Sections 3.7(b) and 3.8 and the last sentence of Section 3.10 are
incorporated into this Sublease), the first sentence of Section 8.3
(Electricity, Water and Gas), Section 8.7 (Representations), Section 9.13
(Assignment and Subletting) (exclusive of Section 9.13(b), which Section 9.13(b)
is incorporated into this Sublease),13.6 (Brokerage), 13.8 (Security Deposit)
and 13.12 (Landlord's Holdover Contribution); (b) Exhibit D (Building
Construction Work), Exhibit E (Tenant's Plans and Specifications), Exhibit G
(Option to Extend, Right of First Offer), and Exhibit J (Plan of First Offer
Space); (c) the definitions "Landlord's Construction Representative", "Tenant's
Construction Representative", "Anticipated Term Commencement Date, "Commencement
Date", "Landlord's Holdover Contribution" and "Tenant's Access Date" in Section
1; and (d) such other definitions in Section 1 and such other terms of the Prime
Lease as are inapplicable, inconsistent with, or specifically modified by the
terms of this Sublease. Provided Sublessee is not in default under this Sublease
beyond applicable periods of notice and grace, Sublessor covenants and agrees
not to voluntarily cancel or surrender the Prime Lease, except for a termination
expressly permitted thereunder as a result of casualty or condemnation.
Notwithstanding the foregoing, the provisions of Section 12.2 of the Prime Lease
are incorporated herein by reference as if set forth herein in full and shall be
applicable to this Sublease as provided above, except that Sublessee shall not
be entitled to receive a recognition or non-disturbance agreement from any
mortgagee or lessor.

         10. Certain Services and Rights. Except to the extent otherwise
expressly provided herein, the only services or rights to which the Sublessee is
entitled hereunder, including without limitation rights relating to the repair,
maintenance and restoration of the Subleased Premises, are those services and
rights to which Sublessor is entitled under the Prime Lease. Sublessor shall
reasonably cooperate with Sublessee in obtaining such services and rights from
the Prime Lessor. Sublessee acknowledges and agrees that Sublessor shall have no
obligation to furnish any services whatsoever to Sublessee, except as expressly
provided in this Sublease, any such obligation being that of the Prime Lessor
under the Prime Lease and that the sole obligation of Sublessor hereunder with
respect to such services is to use reasonable efforts in cooperation with
Sublessee to attempt to cause Prime Lessor to perform its responsibility
thereunder.

         11. Compliance with Prime Lease. Sublessee shall neither do nor permit
anything to be done which would cause the Prime Lease to be terminated or
forfeited by reason of any right of termination or forfeiture reserved or vested
in Prime Lessor under the Prime Lease, and Sublessee shall protect, defend (with
counsel reasonably approved by Sublessor), indemnify and hold Sublessor harmless
from and against any and all claims, liability, loss, damage and expense
(including reasonable attorneys' fees) of any kind whatsoever by reason of any
action or inaction on the part of Sublessee by reason of which the Prime Lease
may be terminated or




                                      -6-
<PAGE>

forfeited. Provided Sublessee complies with the terms of this Sublease,
Sublessor shall not do anything, and Sublessor shall make reasonable efforts not
to permit anything to be done by third parties (including, without limitation,
by any other assignee or Sublessee of Sublessor), which would cause the Prime
Lease to be terminated or forfeited by reason of any right of termination or
forfeiture reserved or vested in Prime Lessor under the Prime Lease, and,
provided Sublessee complies with the terms of this Sublease, Sublessor shall
protect, defend (with counsel reasonably approved by Sublessee), indemnify and
hold Sublessee harmless from and against any and all claims, liability, loss,
damage and expense (including reasonable attorneys' fees) of any kind whatsoever
by reason of any action or inaction on the part of Sublessor (and/or by any
other assignee or Sublessee of Sublessor to the extent Sublessor has not made
reasonable efforts as provided above) by reason of which the Prime Lease may be
terminated or forfeited. Sublessee and Sublessor each hereby covenants and
agrees that it will not do or omit to do anything which would constitute a
default under the provisions of the Prime Lease (provided in the case of
Sublessor, Sublease has complied with the terms of this Sublease) or omit to do
anything which it is obligated to do under the terms of this Sublease, which
would constitute a default under the Prime Lease.

         12. Default. In the event that Sublessee shall default in any of its
obligations hereunder, including any default of the nature described in the
Prime Lease, Sublessor shall have available to it all of the rights and remedies
available to Prime Lessor under the Prime Lease as though Sublessor were the
landlord thereunder and Sublessee the tenant thereunder. Notwithstanding
anything to the contrary contained herein, Sublessee shall be in default of this
Sublease if: (a) Sublessee shall fail to pay Base Rent, Additional Rent or other
charges hereunder when due and such failure shall continue for five (5) days
after receiving notice from Sublessor, or (b) Sublessee shall fail to perform or
observe any covenant contained herein or in the Prime Lease on Sublessee's part
to be performed or observed and such failure shall continue for the period after
receiving notice from Sublessor that is equal to five (5) days less than the
required notice period for such failure under Section 11 of the Prime Lease.
Sublessee further agrees to reimburse Sublessor for all costs and expenses,
including reasonable attorney's fees, incurred by Sublessor in asserting its
rights hereunder against Sublessee or any other party.

         13. Brokerage. Sublessee represents that it has not dealt with any
broker in connection with this Sublease. Sublessee shall protect, defend (with
counsel approved by Sublessor), indemnify and hold Sublessor harmless from and
against all claims for brokerage or commission on account of this Sublease
arising out of dealings by Sublessee with any broker.

         14. Notices. All notices or other communications hereunder shall be in
writing and shall be delivered by hand, or by telecopy or other facsimile
transmissions (followed with a "hard" copy sent by national prepaid overnight
delivery service) or sent by generally recognized over-night courier or by
United States registered or certified mail, postage prepaid, addressed to each
party at the address first set forth above or at such other address as either
party shall hereafter designate by notice to the other. Sublessee shall also
deliver a copy of any notice required to be delivered by Sublessee to Sublessor
hereunder to Sublessor's attorney: Walter R. McCabe III, Ropes & Gray. One
International Place, Boston, MA 02110-2624.


                                      -7-
<PAGE>

Notices shall be deemed given when delivered, or if mailed, on the day deposited
in the mail as herein provided. Sublessor shall also deliver a copy of any
notice required to be delivered by Sublessor to Sublessee to VIRBAC S.A., 1 ere
Avenue-2065 m L.I.D.-06516 Carros France, Attention: General Counsel.

         15. Security Deposit. On the date of execution of this Sublease by
Sublessee, Sublessee shall post with Sublessor (and maintain at all times during
the Term hereof) a Security Deposit in the amount of $ 77,914.02 which shall be
held as security for Sublessee's performance hereunder. Notwithstanding any
provisions to the contrary contained within this Sublease, in the event of the
occurrence of a default by Sublessee under the Prime Lease or this Sublease,
Sublessor may use said Security Deposit to the extent necessary to cure such
default. Upon the use of all or any part of the Security Deposit to cure any
default by Sublessee, Sublessee shall forthwith deposit with Sublessor the
amount of Security Deposit so used, and failure to do so shall be deemed a
default hereunder. Sublessee understands that its potential liability under this
Sublease is not limited to the amount of the Security Deposit. Use of said
Security Deposit by Sublessor shall not constitute a waiver, but is in addition
to other remedies to Sublessor under this Sublease and under law. Such amount
held as a Security Deposit shall bear no interest. If the Sublessee has
fulfilled all of its obligations under this Sublease, any remaining balance of
said Security Deposit shall be returned to Sublessee within thirty (30) days of
the expiration of the Term of this Sublease.

         16. Miscellaneous. This Sublease may be executed in one or more
counterparts which together shall constitute one instrument. The invalidity or
unenforceability of any term or provision hereof shall not affect the validity
or enforceability of any other term or provision hereof. The captions to the
paragraphs hereof are for convenience of reference only and are not intended to
affect the meaning of the provisions of this Sublease. This Sublease is to be
construed as a Massachusetts' contract, is to take effect as a sealed
instrument, supersedes all prior communications between the parties hereto, sets
forth the entire agreement and understanding between the parties and may be
canceled, modified, or amended only by a written instrument executed by both
Sublessor and Sublessee. Terms used herein and not defined shall have the
meaning set forth in the Prime Lease.

         17. Consent of Prime Lessor. This Sublease is subject to the prior
approval and consent of Prime Lessor, which Sublessor agrees to use commercially
reasonable efforts to obtain. This Sublease shall not become effective unless
and until a written consent to this Sublease is executed and delivered by the
Prime Lessor.

         18. Utilities. In the event that Sublessor does not provide utility
services to GTC Biotherapeutics, Inc. ("GTC") pursuant to the terms of the
Sublease dated July 16, 2002 by and between GTC and Sublessor, as amended by
First Amendment to Sublease dated of even date herewith (as so amended, the "GTC
Sublease"), or in the event that Sublessee enters into or is deemed to have
entered into a direct lease with Prime Lessor, Sublessee will (i) maintain the
utility systems that service GTC's premises under the GTC Sublease and (ii)
supply to GTC the utility services that Sublessor is required to supply to GTC,
in each case in accordance with Sublessor's obligations to GTC under the GTC
Sublease.



                                      -8-

<PAGE>

         IN WITNESS WHEREOF, Sublessor and Sublessee have executed this Sublease
as a sealed instrument as of the date first written above.


                          Sublessor

                          ANTIGENICS INC., a Massachusetts corporation and a
                          wholly owned subsidiary of Antigenics Inc., a Delaware
                          corporation

                          By: /s/ Deanna M. Petersen
                              -----------------------------------------------
                              Name: Deanna M. Petersen
                              Title: Vice President, Business Development

                          Sublessee

                          PP MAnufacturing Corporation, a Delaware corporation

                          By: /s/ Pierre PAGES
                              -----------------------------------------------
                              Name: Pierre PAGES
                              Title: President


<PAGE>

                                 Lease Guaranty

The undersigned, Virbac, S.A., a French corporation (the "Guarantor") of which
Sublessee is a wholly owned subsidiary, for good and valuable consideration the
receipt and sufficiency of which is hereby acknowledged and as a duly authorized
corporate action hereby unconditionally guarantees to Antigenics Inc., as
sublandlord (the "Sublessor"), under a Sublease dated as of March 16, 2004 to
which this Guaranty is attached (as from time to time amended and in effect, the
"Sublease") with PPM Manufacturing Corporation, as Sublessee (the "Sublessee"):
(i) the full and prompt payment when due and at all times thereafter of each and
all payments of rent, additional rent and each and all other payments required
to be made by the Sublessee under the terms of the Sublease (whether to the
Sublessor or to such other payee as may be specified in the Sublease); and (ii)
the full and prompt performance and observance by the Sublessee of each and all
of the covenants and agreements of the Sublessee under the terms of the
Sublease. All payments by the Guarantor shall be paid in lawful money of the
United States of America.

         The obligations of the Guarantor under this Guaranty shall be primary,
absolute and unconditional and shall remain in full force and effect until the
Sublessee shall have fully and satisfactorily discharged all of its obligations
to the Sublessor under the Sublease irrespective of (a) the genuineness,
validity, regularity or enforceability of the Sublease or any assignment,
subsublease or termination thereof; or (b) any compromise, settlement, release,
renewal, extension, indulgence, change in or waiver or modification of any of
the obligations and liabilities of the Sublessee under the Sublease or the
release or discharge of the Sublessee from the performance or observance of any
agreement, covenant, term or condition contained in the Sublease by operation of
law or otherwise; or (c) the voluntary or involuntary liquidation, dissolution,
sale or other disposition of all or substantially all the assets, marshalling of
assets and liabilities, receivership, insolvency, bankruptcy, assignment for the
benefit of creditors, reorganization, arrangement, composition or readjustment
of, or other similar proceeding affecting, the Sublessee or any of its assets,
or the disaffirmance of the Sublease in any such proceeding.

         The Sublessor, at its sole election, shall have the right to proceed
first and directly against the Guarantor under this Guaranty without proceeding
against or exhausting its remedies against the Sublessee, and without resorting
to any other security held by the Sublessor. The Guarantor shall also be liable
to the Sublessor for the expense of enforcement of and collection on this
Guaranty including reasonable attorneys' fees.

         This Guaranty and every part hereof shall be binding upon the Guarantor
and its successors and assigns, shall inure to the benefit of the Sublessor and
its successors and assigns and also the Prime Lessor under the Sublease, and may
not be modified or amended without the prior written consent of the Sublessor.
If the Prime Lessor makes an Election under the Consent (as defined in the
Sublease), then the obligations hereunder shall also include all obligations
under the Sublease as amended by the Consent. The terms of this Guaranty may be
enforced as to any one or more breaches of the Sublease either separately or
cumulatively.

         The Guarantor does hereby represent and warrant that:
<PAGE>

         (1) It has power to enter into this Guaranty and has duly executed and
delivered this Guaranty; and neither this Guaranty, the execution and delivery
thereof nor the agreements herein contained are prevented or limited by,
contravene, or constitute a default under, any agreement, instrument or
indenture to which the Guarantor is a party or by which it is bound or any other
requirement of law; and

         (2) The Guarantor is an affiliate of Sublessee and the assumption by
the Guarantor of its obligations hereunder will result in a financial benefit to
the Guarantor.

         The Guarantor hereby waives notice of acceptance hereof and of all
notices and demands of any kind, including without limitation any and all
demands of payment on, and notice of nonpayment, protest and dishonor with
respect to the Sublease. The Guarantor further waives notice and hereby consents
to any amendments of the Sublease and the same shall in no way impair the
undersigned's liability hereunder. Nothing shall discharge or satisfy the
undersigned's liability hereunder expect the full performance and payment of the
obligations guaranteed hereunder. This instrument is a continuing Guaranty and
shall continue in full force and effect and shall not be terminable so long as
the obligations guaranteed hereby, or any modifications, supplements or
amendments thereto shall remain in force and effect.


<PAGE>

          Agreed under seal March 16, 2004.

                                            VIRBAC, S.A., a French corporation

                                            By: /s/ Pierre Pages
                                               _______________________________
                                               Name: Pierre Pages
                                               Title: Director General